Table of Contents

Figure 1. The view of the Tower Crane After Collapse. Photo Courtesy to Peter Stroh.

On March 15, 2008, a tower crane collapsed during the construction of a 43-story concrete framed building at 303 East 51st Street in New York, New York. The crane failure caused seven fatalities and multiple injuries, with extensive damage to the adjacent buildings (McFadden, 2008). The accident was called “one of the city’s worst accidents” by authorities. The collapse occurred at 2:22 p.m., employees were placing lateral tie beams on the 18th floor of the building under construction to provide lateral support to the crane. The crane broke away from its anchors and toppled south, across the block between 51st and 50th Streets. Figure 1 shows the view of the tower crane after the collapse. Upon investigation, the primary cause of the collapse was the polyester slings holding the collar at the 18th floor failed. Improper usage of the polyester slings resulted in the failure of the slings.

Keywords

303 East 51st Street is a proposed 43-story concrete framed residential building located on the East Side of Manhattan in New York. The building is designed by Garrett Gourlay Architect PLLC on behalf of Kennelly Development Company, LC. The construction started in 2007 and was put on-hold status since the crane collapse happened on March 15, 200. The 19th floor deck was just poured prior to the collapse. The crane used during construction was an external self-climbing luffing tower crane, Model M440E, manufactured by Favelle Favco Cranes Pty. Ltd. and provided by New York Crane of New Jersey (NYC DOB, 2009). The total height of the crane at its largest expansion was 472 ft. At the time of the collapse, the crane was approximately 250 ft. The tower crane was used until the floor-to-tower connections were placed at both the 3rd and 9th floor. Each floor-to-tower connection consisted of a two part steel framed collar surrounding the tower and three W12x79 tie-beams connected via pins to each completed collar. The far end of each tie-beam was welded to a steel base plate, which was in turn anchored by bolts to the reinforced concrete slab of the building, thus fixing the tie-beam to the building. Figure 2 shows the schematic of the crane (Right) (NYC DOB, 2009) and the plan view of the collar assembly (Left) (Cohen, 2009).

Figure 2. Schematic of the crane (Right) and the plan view of the collar assembly (Left). Based on the drawing provided by Arup Inc. and the rendering provided by Cohen, 2012

Collapse

Figure 3. The View of the Tower Base After Collapse. Photo Courtesy to New York County District Attorney.

On March 15, 2008 from 7:00 am, the tower crane was “jumped” or extended the height of 18th floor. The collar halves were lifted, bolted together and suspended from the tower while the first tie-in beam was installed. The collar was suspended from the tower by four polyester web slings. However, the polyester web slings failed and the collar fell downwards along the tower. The 18th floor collar struck the 9th floor collar below and destroyed the connection, thus causing the failure of both collars. The 3rd floor collar was deflected and bended due to the failure of the collars above (NYC DOB, 2009). With lateral remaining at Level 3 and the base only, the tower overturned as its base slid towards the building structure to the north. The upper section of the crane, including the cabin and jib, split off the boom and fell towards south. Part of the crane fell on a 19-story residential building on 300 East 51st Street and the other part crushed a 4-story town house on 50th street. Figure 3 shows the view of the tower base after collapse (NYC Buildings, 2008).

Investigation and Findings

A number of parties were involved in the investigation, including the New York City Department of Investigations (NYCDOI), the New York County District Attorney (NYCDA) and the U.S. Department of Labor, Occupational Safety and Health Administration (OSHA). Due to the criminal investigation, there were additional technicalities imposed on the investigation besides the forensic engineering investigations involving potential civil lawsuits (Cohen, 2012). Arup Inc. was hired by the New York City Department of Buildings (NYCDOB) to provide engineering investigations. The forensic engineering investigations activities included document review, site visit to the collapse site and to view components of the tower crane and the collar assemblies, structural analysis of the tower crane and the sling system, and material testing.

Based on the investigations, the failure of the polyester web slings supporting the steel collar at 18th floor level was found to be the initiative of collapse of the tower crane (Arup, 2009). The failure of the slings was resulted from improper usage of the slings, which included:

Inadequate number of slings. The crane manufacturer required eight web slings to provide enough supports to the steel collar while only four web slings were used in this case;

Improper connection of the sling. The slings which were used to lift the collar halves had been incorrectly attached to the collar using the chain block attachments and the two slings used to suspend the collar from the tower were attached to the lifting point lugs, rather than the designated chain block lugs, which was inconsistent with industry practice and standard. Furthermore, no padding was used to protect the polyester web slings from the unprotected edges of the tower legs around which they were slung. Figure 5 shows the specified sling lifting points and the sling lifting points used in this case, which caused the choking of the slings against unprotected edges (NYC DOB, 2009, pp. 213).

One of the slings which was located at the southwest corner of the tower, was already frayed and deteriorated before it was used to support the collar.

The improper installation of one sling lead to a sudden and uneven redistribution of load to the remaining three slings and caused the failure of the remaining slings, thus allowing the collar to fall from Level 18. The unanticipated loads arising from the dynamics of the collar falling from Level 18 caused failure of the collar connection at Level 9, which in turn allowed slippage of the steel at the base of the crane resulting in the overturning of the tower.

Aftermath

Based on the investigation findings, the indictment of the tower crane rigger William Rapetti, and his company was announced on multiple charges of manslaughter, criminally negligent homicide, assault, and reckless endangerment (NYC Buildings, 2009). An inspector with the Department of Buildings was arrested shortly after the collapse on charges that he filed a report of fake inspection the day before the collapse (Eligon, 2009). Department of Buildings inspectors performed a citywide safety inspection of all tower cranes undergoing jumping operations. Of the 18 jumps performed, Inspectors found that all were in compliance with new crane safety laws enacted last year: all contractors held the required safety meetings before their operations began, all provided detailed rigging plans on site during the inspections, and synthetic slings were not used during any operation. During 2009, 12 new laws were enacted to increase construction safety and regulatory oversight. The major updates include the use of nylon slings. The use of nylon slings should only be used if the manufactures provide specified instructions. Nylon slings should never be used unless softening mechanisms have been applied (NYC Buildings, 2009).

Lessons Learned

Industry Regulation and Local Law

Regulation is one of the most important factors to prevent disasters like this. At the time of the collapse in 2008, OSHA’s crane and derrick rules dated back to the standards of the 1960s and were no longer reflective of new crane designs and industry practices. For example, synthetic slings were not even used in the 1960s (Parfitt, 2009). In 2010, OSHA issued the new crane and derrick rules. One key provision requires that crane operators must be certified and other crane-related workers including riggers must be qualified. The new provision will become effective in 2014.The new regulations also include provisions dealing with synthetic slings, which requires synthetic slings to be used in accordance with manufacturers’ instruction during assembly and disassembly (Ichniowski, 2010). While the new OHSA rules provide industry standards for crane safety, the local regulations need to be updated in response to various crane accidents based on their own situations. However, it is important to keep the local law inconsistent with the industry regulations.

Inspections

The investigation of the 51st street crane collapse also found that the crane inspection and permitting protocols failed to identify the rigging errors that caused the collapse. The tower crane was just inspected on March 14, 2008, the day before the collapse. The inspectors with the Department of Building inspected the mast sections of to be used to jump the crane but no violations were issued as a result of that inspection. Before that inspection, the crane was also inspected on March 4, when building inspectors scrutinized the crane in response to a complaint and found it to be erected correctly (NYC Buildings, 2008). When the regulation and rules are established, it is in great need to ensure there are enough qualified inspectors to perform the inspections.

Quality Control

From the construction company standpoint, it is more effective to take measures on proactive quality control (Shapira and Lyachin, 2009). Project-level quality control, including actions to increase crane-related awareness, training, preventive actions, monitoring, inspection, and rewards and punishment, will reduce the chances of crane accidents. Company-level safety management is established to make sure adequateness of the resources allocated to crane safety.

Similar Cases

On May 30, 2008, another tower crane collapse occurred at 91st Street and First Avenue when the city was issuing new rules regulating crane operations and inspections. The collapse resulted in the death of the crane operator and a construction worker, with severely damaged several high-rise buildings. The cab and boom separated from the upper section of the tower and fell against the adjacent building. Instead of installation errors, the weld along the circumference of the turntable was the initiation of the collapse (Grynbaum, 2008). The collapse occurred just two days after the city relaxed some of the rules it had put in place after the March accident.

Conclusions

Tower cranes are the most conspicuous symbol of today’s typical construction sites, especially in the construction of high rise buildings (Beavers et al., 2006; Peraza and Travis, 2009). However, it is also one of the most dangerous equipment. Increasing attention has been focused on the safety of crane recently due to the increasing number of crane failures and accidents. While efforts on industry regulations and local laws have been made to improve the crane safety, there are more needs to be done on the inspection side to make sure the implementation of the regulation and rules. The construction company should also pay enough attention to the crane safety issues, establishing company-level and project-level management rules are effective measures to reduce crane failures or accidents.

Bibliography

Beavers, J.E., Moore, J.R., and Schriver, W.R. (2006). “Crane Related Fatalities in the Construction Industry.” Journal of Construction Engineering and Management, 132(9), 901-910.This journal paper examined the OSHA’s case files from fatality investigations during 1997-2003 and summarized the proximal causes and presents suggestions in order to reduce the rate of crane fatalities.

Cohen, J.S. (2012) “51st Street Crane Collapse: Issues in the Investigation during Criminal Proceedings”, Forensic Engineering, 2012, 342-350.
This journal paper describes the investigation carried out by Arup and the limitations imposed by the criminal proceedings.

NYC Department of Buildings. (March 2009). "51st Street Crane Investigation." New York City Department of Buildings,<http://www.nyc.gov/html/dob/downloads/pdf/51streetcraneinvestigation_all.pdf>, (September 30, 2013).Arup was hired by the New York City Department of Buildings to investigate the cause of the accident. This report provides the detailed investigation approach and the key findings of the investigation.

Parfitt, M.K. (March 2009). "Cranes, Structures under Constuction, and Temporary Facilities: Are We Doing Enough to Ensure They are Safe?" Journal of Architectural Engineerin.This article discusses the prevention of crane failures from an industry-wide perspective.

Peraza, D.B., Travis, J. A. (2009). “Crane Safety-an Industry in Flux.” Forensic Engineering, (2009), 556-566.This paper and summarize new regulations at local and national levels based on the review crane accident statistics and the causes of milestone crane accidents.

Shapira, A. and Lyachin, B. (2009). ”Identification and Analysis of Factors Affecting Safety on Construction Sites with Tower Cranes.” Journal of Construction Engineering and Management, 135(1), 24–33.This paper identifies the major factors affecting safety in tower crane environments and evaluated the degree to which each factor influences ongoing safety on site.

Additional Bibliography

Ayub, M. (September 2008). “Investigation of the March 15, 2008 Fatal Tower Crane Collapse at 303 East 51st Street, New York, NY.” Occupational Safety & Health Administration.This report explains OSHA's investigation results right after the crane collapse. The results were consistent with the investigation results of Arup. This case study uses the investigation results of Arup with a comparison of the OSHA's results.